This invention relates to a breather cap for closing an unthreaded spout or filler tube.
Hydraulic reservoirs, transmission cases and the like normally have a filler tube or spout for adding oil or other liquids thereto. The filler spout is normally closed by either a vented or nonvented closure cap. In some uses, hydraulic reservoirs, transmission cases, etc. must be vented to ambient to prevent buildup of pressure or the formation of a vacuum therein due to, for example, expansion and contraction of the liquid in response to temperature changes of the liquid, or due to an increase or decrease in the volume of liquid in response to retraction and/or extension of a hydraulic jack. Thus, when a nonvented cap is used, a separate breather must be provided thereby increasing the manufacturing cost, and in some cases the breathers are prone to permit excessive leakage of the liquid. Although the vent caps heretofore available are less prone to leakage, they have required additional machining steps such as threads on both the filler tube and closure cap.